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22 12 Deidre investigates the humus content of soil. She weighs different soil samples that have been dried in an oven. Deidre then burns each soil sample using a Bunsen burner. She continues to burn them until there is no change in mass.

soil being heated from the top

Deidre records her results in a table. Soil sample

Mass before burning in g

Mass after burning in g

Change in mass in g

Percentage change in mass

A

56.65

48.52

8.13

14.35

B

55.34

54.32

1.02

1.84

C

56.10

54.36

D

55.42

51.98

3.44

6.21

(a) The soils needed to be dry before they were burnt. Suggest why. ................................................................................................................................................... ............................................................................................................................................. [1] (b) Calculate the percentage humus content of soil C.

answer ......................... %

Š OCR 2013

[2]

B6 question 12 (1)  
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